1. Field of the Invention
The present invention primarily applies to the medical device field, and more particularly, pertains to an immersion bag system having an immersion bag of acoustically invisible material and a flexible sealing collar which when engaged with a body of an ultrasound probe forms a deformable valve which can also serve as a pressure release valve. The bag encapsulates the distal end of and is incorporated into use with an ultrasound probe. The immersion bag system, suitable for containment of a gel or other aqueous medium of any suitable viscosity, overcomes near field artifact allowing the examination of shallow anatomical structures. In operation of the invention the distal end of the ultrasound probe, including a transducer, is immersed in the gel or other aqueous medium.
Definition of “near field artifact”. Typically, a stationary ultrasound probe passes or scans over just 10 degrees during ultrasound scanning, but by physically moving the ultrasound probe transducer head back and forth via a motor or other suitable means, a range of 120 degrees can be examined. However, when the ultrasound probe transducer head moves, the consequential pulsating of the ultrasound waves collide with one another creating interference which results in an acoustic dead zone. Structures contained within this dead zone cannot be visualized and this is termed “near field artifact”. Therefore, examining shallow/superficial tissue with a moving ultrasound probe, anatomical structures within the near field artifact cannot be visualized because of the near field artifact.
This invention has medical and industrial applications by enhancing the ability to exam shallow/superficial structures amenable to ultrasound evaluation. Medical and industrial sonogram examinations may be improved by this method of overcoming near field artifact (defined previously). This includes:                a. anterior ocular structures, e.g., the cornea, iris, iris angle, lens, ciliary body;        b. skin lesions, e.g., skin cancers, cysts, or neoplasms;        c. vascular structure/flow assessment; and,        d. industrial monitoring of flow characteristics in tubing.        
2. Description of the Prior Art
Ultrasound scans of the eye or other areas of the body are performed using an ultrasound probe and a coupling medium placed between the ultrasound probe tip and the surface of the area being scanned during examination. The medium, such as a gel or other less viscous aqueous medium, allows for the transmission of ultrasound waves between the ultrasound probe and through human tissue or other structures. To reduce or eliminate the near field artifact, the ultrasound probe tip and the superficial structures under examination, such as blood vessels or anterior aspects of the eye, must be separated at a distance from each other and not in direct contact. A common method of accomplishing this is to use a cylindrical shaped cup that is open on both ends which can contain gel or other suitable aqueous medium and which is placed over the area of the examining surface. The use of an open cylindrical shaped cup requires that the operator fill the cup with gel or other suitable aqueous medium. An excessive filling of the cup may result in undesirable overrun of the cup when the tip of the ultrasound probe is introduced therein and the coupling gel, e.g., methylcellulose, may be an eye irritant. An insufficient filling of the cup results in less than desirable ultrasound scan examination because the near field artifact opaque zone cannot be overcome, thus preventing an examination of the structure under study. More importantly, if a cylinder with an open bottom, i.e., a cup, is used, the gel or other suitable aqueous medium must be at a depth to allow a sufficient probe distance from the exam surface to overcome the opaque zone created by the near field artifact. The acoustically transparent immersion bag of the present invention eliminates the need for tedious and correct medium filling to a proper level and provides for ultrasound probe separation from the exam surface to overcome the near field artifact, thereby allowing visualization of superficial structures of the body and/or other structures during the ultrasound exam. Further, with the open cylinder technique, the ultrasound probe may readily come into contact with the sensitive cornea of the eye. Transmission of microorganisms is possible with the open cylinder technique as sterilization of the ultrasound probe is difficult and time consuming.